I want to calculate 2^64-1 which is
18446744073709551615
I set the following options to prevent scientific notation
options("scipen"=100, "digits"=4)> x<-2^64 -1
> x
[1] 18446744073709551616
This is not correct. There seem to be still some approximation happening.
How can I get the correct result?
Yousri
IBM Canada ltd
Software developer
[[alternative HTML version deleted]]
The largest consecutive integer that can be represented in double precision is 2^53. You'll have to move past double precision. ---JRG On 2020-11-13 20:44, Yousri Fanous wrote:> I want to calculate 2^64-1 which is > 18446744073709551615 > > I set the following options to prevent scientific notation > options("scipen"=100, "digits"=4) >> x<-2^64 -1 >> x > [1] 18446744073709551616 > > This is not correct. There seem to be still some approximation happening. > How can I get the correct result? > > Yousri > IBM Canada ltd > Software developer > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >
You need the Rmpfr package. Your calculation of 2^64 is an ordinary double precision number with 53 bits of precision.> library(Rmpfr)Loading required package: gmp Attaching package: ?gmp? The following objects are masked from ?package:base?: %*%, apply, crossprod, matrix, tcrossprod C code of R package 'Rmpfr': GMP using 64 bits per limb Attaching package: ?Rmpfr? The following object is masked from ?package:gmp?: outer The following objects are masked from ?package:stats?: dbinom, dgamma, dnorm, dpois, pnorm The following objects are masked from ?package:base?: cbind, pmax, pmin, rbind> class(2)[1] "numeric"> class(2^32)[1] "numeric"> class(2^64)[1] "numeric"> Two <- mpfr(2, precBits=64) > Two^641 'mpfr' number of precision 64 bits [1] 18446744073709551616> class(Two^64)[1] "mpfr" attr(,"package") [1] "Rmpfr"> Two^64 - 11 'mpfr' number of precision 64 bits [1] 18446744073709551615> getPrec(Two)[1] 64> getPrec(2.)[1] 53>On Fri, Nov 13, 2020 at 8:45 PM Yousri Fanous <yousri.fanous at gmail.com> wrote:> > I want to calculate 2^64-1 which is > 18446744073709551615 > > I set the following options to prevent scientific notation > options("scipen"=100, "digits"=4) > > x<-2^64 -1 > > x > [1] 18446744073709551616 > > This is not correct. There seem to be still some approximation happening. > How can I get the correct result? > > Yousri > IBM Canada ltd > Software developer > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.
Hello, You can compute the exact result with package Rmpfr. See ?mpfr and [1]. library(Rmpfr) two <- mpfr(2, precBits = 64) two^64 - 1 #1 'mpfr' number of precision 64 bits #[1] 18446744073709551615 [1] https://www.mpfr.org/ Hope this helps, Rui Barradas ?s 01:44 de 14/11/20, Yousri Fanous escreveu:> I want to calculate 2^64-1 which is > 18446744073709551615 > > I set the following options to prevent scientific notation > options("scipen"=100, "digits"=4) >> x<-2^64 -1 >> x > [1] 18446744073709551616 > > This is not correct. There seem to be still some approximation happening. > How can I get the correct result? > > Yousri > IBM Canada ltd > Software developer > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >
Hello, I forgot to suggest package gmp. See the second example in ?gmp::bigz Hope this helps, Rui Barradas ?s 05:50 de 14/11/20, Rui Barradas escreveu:> Hello, > > You can compute the exact result with package Rmpfr. > See ?mpfr and [1]. > > > library(Rmpfr) > > two <- mpfr(2, precBits = 64) > two^64 - 1 > #1 'mpfr' number of precision? 64?? bits > #[1] 18446744073709551615 > > > > [1] https://www.mpfr.org/ > > Hope this helps, > > Rui Barradas > > ?s 01:44 de 14/11/20, Yousri Fanous escreveu: >> I want to calculate 2^64-1 which is >> 18446744073709551615 >> >> I set the following options to prevent scientific notation >> options("scipen"=100, "digits"=4) >>> x<-2^64 -1 >>> x >> [1] 18446744073709551616 >> >> This is not correct. There seem to be still some approximation happening. >> How can I get the correct result? >> >> Yousri >> IBM Canada ltd >> Software developer >> >> ????[[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.